Y'all, don't be hatin on each other. Neither of you has any definitive proof, so how about we wait until Word of God confirms something?

It's in the same multiverse, like the DC comics. Superman is never in the same world as Batman, until something universal requires it.
There are running themes between the worlds (superhumanity, moral breakdown, insanity...), but they are different worlds. Recent example: Penumbra and Amnesia.

The time frames just don't seem to match up. Also, if there was that kind of magic juice out there before, why is none seen in Rapture? Why are Plasmids required if they are so effective?

But both Rapture and Colombia are extremely isolated communities; is it any wonder that they might have entirely unique technologies?

Colubia ain't.
"Columbia is like the moon landing of 1900, it's a demonstration of power." -Ken Levine
http://www.youtube.com/watch?v=KDft7dC6Foo

Columbia is about as isolated as the moon. Just because it's not as secretive as Rapture doesn't mean that it's a clone of Infinite-era America or vice versa.

Doesn't mean they can't share stuff with the ground, though.
They do interact with "foreigners", as seen by Communist Bot.

Rapture is still pretty unique in of itself in the sense that it's just a conglomeration of scientists/inventors making stuff specifically for Rapture. Vending Machines, Big Daddies, and Security Bots didn't exist before, after all, they were all invented for use in Rapture exclusively. Very little of Rapture's tech is 'borrowed', so to speak.

I think the other cool element is the complete sense of isolation from the outside world. I'm pumped for infinite, though. Gotta play through BS2 first.

looks like its gonna be better than the first two imo

The original bioshock was more of an exploration and wonderment type of game. I loved that because of never knowing what that damn heavy breathing shadow was around the corner. Part of the fun was taking my time and exploring the weird crap everywhere, anyone could rush through the game if they wanted to.

This one seems a hell of a lot more scripted, which is fine, if the game's going to be a longer one. I still want time to explore weird parts and try to figure out what Columbia's all about. Just don't know if I'm going to be able to with those zip-lines and constant scripted scenes.

i haven't had time to read all 72 posted but heres something i found thats funny and goses on the theme of Bioshock Infinite LITERAL.

http://www.youtube.com/watch?v=LSCswCg-9gk

Elizabeth looks pretty damn healthy for someone imprisoned for fifteen years.

I never really paid attention to bioshock, but reading some of the stories makes want hack away at it. Though I kind of dislike the rpg style in the missions.